Here’s how a border wall would impact the environment – from fauna to the flow of rivers.

President Donald Trump took the national stage last night to make his case for the construction of a wall at the US-Mexico border. But experts say such an enormous construction project would have significant impacts on the environment around the nation’s southern border.

His live address from the Oval Office came 18 days into a partial government shutdown, which is the result of a disagreement over funding for Trump’s desired border wall. The shutdown has impacted nearly 800,000 federal employees (and caused garbage to pile up in national parks), but Trump has indicated that he won’t end the shutdown until he secures $5 billion in funding for the wall.

Trump most likely intended for his national address to boost public support for a wall – despite the environmental impact.

No new barriers have been erected yet, but Congress approved about $1.6 billion in 2017 to put towards border projects. That money was allocated mostly for fortifying existing fencing, as NPR noted.

In the effort to build a new, 1,000-mile section of the border wall, President Trump authorized contractors to build eight prototypes from a range of materials.

The carbon emissions from constructing Trump’s proposed 1,000 miles of new border wall could top 7.8 million metric tons, according to MIT Technology Review.

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A section of the US-Mexico border fence at Sunland Park, opposite the Mexican border city of Juarez, January 26, 2017.

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REUTERS/Jose Luis Gonzalez

Every cubic meter of concrete that’s poured into a wall or structure results in roughly 380 kilograms of carbon dioxide emissions, according to a study from the University of Bath in the UK. Producing 1 kilogram of steel also emits 1.8 kilograms of carbon dioxide, according to MIT Technology Review.

Based on those numbers, MIT Tech Review calculated how much carbon dioxide would be emitted total from the construction of a 1,000-mile wall. (By their estimate, it’d be 50 feet tall with an additional 15 feet underground, and one-foot thick.)

Such a wall would need 9.7 million cubic meters of concrete and 2.3 billion kilograms of steel. So in total, that’d create 7.8 million metric tons of carbon dioxide – the equivalent of 877,686,508 gallons of gasoline, according to the Environmental Protection Agency.

But if animals couldn’t travel back and forth between habitats and resources on either side of the border, many species would face local extinction in the US.

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A border wall might prevent the endangered Peninsular bighorn sheep — which has an expansive home range — from traveling between California and Mexico.

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Sam Antonio Photography

The US-Mexico border is nearly 2,000 miles long and peppered with marshes, deserts, and grasslands. The construction of a continuous wall could therefore harm species who are, of course, not on the administration’s immigration radar.

More than 1,500 species of flora and fauna, like the Peninsular bighorn sheep shown above, make their homes along this biologically diverse strip of North America. Sixty-two of these species are considered vulnerable, endangered, or critically endangered by the International Union for Conservation of Nature (IUCN). And many of those species would face extirpation – meaning local extinction in the US – if they were unable to access habitats and resources on either side of the border, according to a study from Stanford University.

The Stanford analysis showed that 346 species would lose access to half of their habitat because of a border wall.

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Getty Images

Of those species, 17% would be stuck living in an area of roughly 7,700 square miles or less – elevating their risk of extirpation, according to IUCN guidelines. According to the study, which was published in the journal BioScience in July 2018, some of these at-risk species include the endangered jaguar and ocelot.

The two Stanford biologists behind the study, Paul Ehrlich and Rodolfo Dirzo, explained that physical barriers – whether they are rivers, mountains, or a human-made wall – can deter or prevent animals from finding mates, fresh water, and necessary food.

Animal migration patterns — even those of birds — would be disrupted.

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Even low-flying birds like the Ferruginous pygmy owl could be impeded by a border wall.

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Fawn Simonds/Getty Images

Dirzo and Erhlich noted the border wall could also impede flying species that enjoy riding currents close to the ground. Examples include the ­endangered Quino checkerspot butterfly or the ferruginous pygmy owl.

Echoing those concerns, the National Audubon Society, the National Resources Defense Council, and more than 170 conservation groups penned a letter to Secretary of Homeland Security Kirstjen Nielsen in November.

The letter elaborated on the impact of a wall on “environmentally sensitive conservation areas” like the Lower Rio Grande Valley area, which has a plethora of butterfly and bird fauna. Bruce Stein, chief scientist at the National Wildlife Federation, wrote, “barriers like border walls can interfere with the ability of animals to meet their daily needs, make seasonal migrations or disperse to new areas.”

Rising temperatures and extreme weather are already altering certain regions’ ecology, leading animals to shift their behavior in order to survive and find food. A wall could prevent creatures from successfully adapting. Stein also pointed this out in the letter to Neilson.

One of the greatest potential environmental impacts of a border wall would be almost invisible at first: it would lead species to become less resilient to stress.

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A US border patrol agent looks over the Rio Grande river at the border between United States and Mexico in Roma, Texas, May 11, 2017.

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REUTERS/Carlos Barria

A wall that cuts animals’ habitat into pieces would consequently force their populations into smaller subgroups that are effectively unable to interact and mate with one another.

That would make each remaining subgroup more vulnerable to diseases and natural disasters. Plus, less gene flow between individuals within a species means less genetic diversity, and a higher possibility of inbreeding. Overall, these consequences would increase a species’ overall risk for extinction.

Conservationists are particularly concerned about the future of the Mexican gray wolf.

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As of 2016, only 113 Mexican gray wolves lived in the US.

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Vichai Phububphapan/Getty

According to Vox, fewer than 200 total Mexican gray wolves remained in the wild in the US and Mexico in 2016. A report from the Center for Biological Diversity in July 2018 noted that the US population of Mexican gray wolves increased by only four individuals between 2014 and 2017. In the report, Bryan Bird, Defenders of Wildlife’s southwest program director, said that the “Mexican gray wolves are in a race with extinction, and the clock is ticking.”

A wall separating the some three dozen wolves in Mexico from their counterparts in the US could therefore be a deadly blow for the world’s most endangered wolf.

A border wall would also change the flow of major rivers.

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The border wall would have to bisect the Rio Grande, which divides Texas and Mexico.

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Deb Snelson/Getty Images

Impacts on wildlife aside, the proposed border wall could also impact the quotidian movements of three major rivers and their tributaries.

The wall would need to bisect the Rio Grande, Colorado, and Tijuana Rivers. Bob Irvin, president of the environmental group American Rivers, told News Deeply that between 100 and 500 rivers and streams would be affected.

The wall would “undoubtedly change the flow of those rivers and streams, and it would also impair the water quality in them,” he said.

Irvin added that “when you change the flow of a river, you’re changing the natural cleansing mechanisms of that river. So you certainly could see a buildup of pollutants – both solid and chemical – as a result of that.”

Depending on where and how a wall were erected — in the middle of a river, say — it could even act like a dam.

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Workers set up concertina wire on the border between Mexico and the US on the Tijuana river, November 26, 2018.

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Alkis Konstantinidis/Reuters

If the border wall wound up acting as a 2,000-mile dam, debris could pile up any time there was a storm, impeding the flow of the river. Irvin told News Deeply that’s already happening along some sections of wall that already exist in Arizona.

According to a report by the Sierra Club, such walls have contributed to severe flooding and flood damage before when constructed across natural drainage points.

One example of such flooding was a 2008 disaster that happened along the US-Mexico border in Nogales, Arizona.

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A continuous border wall could contribute to deadly flooding.

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Ana Maria Serrano/EyeEm/Getty Images

During a seasonal rain storm, that wall acted as a dam, flooding the sister cities of Nogales and Sonara in 6 feet of water. The disaster caused $8 million in property damage and two deaths. Six years later, a similar flood happened again in Nogales, when debris blocked a 60-foot section of the border.

There’s little evidence that the designs for the proposed continuous border wall would account for mitigation of possible flood risks. Quartz even reported that 8 miles of the planned wall in Texas would be built on a floodplain.

“We are extremely concerned that CBP does not appear to be conducting this project in compliance with NEPA [the National Environmental Policy Act] or other applicable federal laws,” they wrote.

The border wall could have other impacts as well, like imperiling water-sharing agreements.

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Roughly 30 bird species living in the Rio Grande Valley don’t live anywhere else in the United States.

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Gallo Images/Getty

A new barrier between the US and Mexico could also affect water sharing agreements between the two nations.

Equitable sharing of the Rio Grande and Colorado rivers is imperative to agriculture, fracking, and energy production in both countries, According to a report by the Brookings Institution. US-Mexican cooperation around water use has benefited both countries, but those agreements could now be at risk.

The wall could also disrupt designated conservation areas. The wall’s proposed path initially sent it barreling through the Santa Ana National Wildlife Refuge, though environmental activists convinced lawmakers to leave the refuge untouched for now. The National Butterfly Center, a state park, could still be threatened.